Reactor with primary and secondary channels

ABSTRACT

An improved reactor comprises primary channels connected by secondary channels. Primary and secondary channels are of orientations and dimensions as to cause fluid to flow through the primary and secondary channels. Catalyst may be coated on the inside of the secondary channels.

FIELD OF INVENTION

This invention is in the field of catalytic reactors.

BACKGROUND

Catalytic reactors are known which comprise an inlet, an outlet, areactor chamber and a monolithic structure. The monolithic structure isplaced within the reactor chamber and a catalytic material is coated onthe monolithic structure.

FIG. 1 is a cutaway view of one prior art reactor 100. An example may befound in FIG. 3 of U.S. Pat. No. 5,330,728 to Michael Foster.

The reactor comprises primary channel walls 102 of the monolith andreactor chamber walls 104. The primary channel walls are parallel toeach other and to the reactor walls. The primary channel walls formprimary channels 103.

The primary channel walls form a monolithic structure wherein eachprimary channel has a square cross section.

The primary channel walls are coated with a catalyst.

In operation, reactant fluid 110 is caused to flow into the primarychannels, react with the catalysts on the primary channel walls and thenexit. As used herein unless otherwise specifically indicated orindicated by context, double line arrows indicate fluid flow.

One of the disadvantages of this prior art is that no means is providedto mix the fluids entering different primary channels. Thus if onechannel gets a high flow 122 of fluid, said fluid will have a shortresidence time and hence less reaction with the catalyst than theaverage fluid. Similarly, if one channel gets a low flow 124 of fluid,then it will have more reaction with the catalyst than the averagefluid. Thus a reactor may have to be oversized to account for thedifference in fluid flows through different channels.

Another disadvantage of this prior art is that fluids often form alaminar flow as they pass down the primary channels. Thus the fluid 150passing down the center of a primary channel will have a higher velocityand lower residence time than the fluid 154 passing down next to thewalls of the channel. Thus a reactor may have to be oversized to accountfor the different fluid residence times of the laminar flows near thewalls and near the center of primary channels.

Furthermore, this prior art has no means of convective heat transferfrom the center of the monolith to the reactor walls.

FIG. 2 is a cutaway view of alternate prior art reactor design 200. Anexample of this prior at is illustrated in FIG. 2 of U.S. Pat. No.5,051,241 to William Pfefferle.

The reactor comprises primary channel walls 202 and reactor walls 204.The primary channel walls are parallel to each other and traverse thereactor. The primary channel walls form primary channels 203. Both endsof all of the primary channels are blocked by the reactor walls.

Secondary channels 206 are provided in the primary channel walls toallow inlet fluid 210 to pass therethrough.

Primary channel walls may be a woven wire mesh where the secondarychannels are the openings in the mesh. Catalyst is deposited on thewalls of the wire forming the wire mesh. Catalyst thus coats both theprimary channel walls and the secondary channel walls.

One of the disadvantages of this prior art is that there is a relativelyhigh pressure drop as fluid proceeds from one primary channel wall tothe next primary channel wall.

SUMMARY OF THE INVENTION

The Summary of the Invention is provided as a guide to understanding theinvention. It does not necessarily describe the most generic embodimentof the invention or all species of the invention disclosed herein.

The invention is an apparatus for carrying out reactions of fluid at acatalytic substrate whereby primary channels are formed at an angle to areactor wall such that at least one primary channel is open at eitherit's inlet or outlet and closed at it's opposite end. Secondary channelsperforate the primary channel walls such that fluid can pass into or outof the at least one primary channel with it's inlet or outlet blocked.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cut away view of one example of prior art.

FIG. 2 is a cut away view of another example of prior art.

FIG. 3 is a cut away view of one embodiment of a reactor according tothe present invention.

FIG. 4 is a cut away view of an alternate embodiment of the presentinvention.

FIG. 5 is a cut away view of another alternate embodiment of the presentinvention.

FIG. 6 is a cut away view of another alternate embodiment of the presentinvention.

FIG. 7 is a cut away view of another alternate embodiment of the presentinvention.

FIG. 8 is a cut away view of another alternate embodiment of the presentinvention.

FIG. 9 is a cut away view of another alternate embodiment of the presentinvention.

FIG. 10 is a cut away view of another alternate embodiment of thepresent invention.

FIG. 11 is a cut away view of another alternate embodiment of thepresent invention.

FIG. 12 is a cut away view of another alternate embodiment of thepresent invention.

FIG. 13 is a cut away view of another alternate embodiment of thepresent invention.

FIG. 14 is an illustration of a secondary channel.

FIG. 15 is an illustration of several alternative secondary channels.

FIG. 16 is a partial cutaway view of the present invention illustratingprimary and secondary channels.

FIG. 17 is a partial perspective cut away view of an embodiment of thisinvention comprising a monolith of frustoconical corrugated layers.

FIG. 18 is a partial perspective cut away view of an embodiment of thisinvention comprising a monolith with radial layers of corrugationinclined at an angle.

FIG. 19 is a perspective view of an embodiment of the inventioncomprising restricted but not blocked primary channels.

FIG. 20 is a plan view of a construction technique for the monolith ofFIG. 18.

FIG. 21 is a plan view of a formation technique for the corrugatedsheets of FIG. 20.

FIG. 22 is a longitudinal section of a portion of a monolithillustrating the flow of fluid through secondary channels.

FIG. 23 is a plan view of a corrugated sheet to be used in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description discloses various exemplaryembodiments and features of the invention. These exemplary embodimentsand features are not meant to be limiting.

FIG. 3 illustrates a longitudinal cross section of embodiment 300 of thepresent invention. Embodiment 300 comprises reactor walls 304 andmonolithic catalyst support 301. The monolithic catalyst supportcomprises primary channel walls 302 which form primary channels 306. Theprimary channel walls are inclined at angle 312 of more than 0° and lessthan 90° relative to the reactor walls such that at least one primarychannel 307 has one end blocked by reactor wall 304. The other end of atleast one primary channel 307 is open. Other conventional means, such asa plug, may be used to block the end of a primary channel.

The primary channel walls comprise secondary channels 308. The secondarychannels allow at least a portion 350 of fluid 310 entering the monolithto flow from one primary channel to an adjacent primary channel.

Catalyst is coated on the walls of the secondary channels. Thus, asubstantial amount of the reaction in the monolith takes place insidethe secondary channels. The primary channel walls may also be coatedwith catalyst.

Suitable inlet fluids include the exhaust gas from an internalcombustion engine. Suitable catalysts include noble metal catalystsincluding platinum group metals. Suitable materials for the monolithinclude ceramics, such as alumina or cordierite, and metals, such asstainless steel.

Suitable inlet fluids can also include blends of natural gas and waterused to produce hydrogen by steam reforming. Known catalysts, materialsof construction, operating temperatures and pressures may be used forsteam reforming.

Explanation

While not being held to this explanation, it is believed that thecombination of primary channels connected by secondary channels withinsaid primary channel walls in the presence of a pressure differentialfrom one side of the said primary channel wall to the other side of theprimary channel wall causes at least a portion 350 of fluid 310 enteringthe monolith to preferentially flow from one primary channel to anadjacent primary channel. This cross flow of fluid disrupts boundarylayers along the primary channel walls thus helping to increasesolid-fluid reactions and create well mixed fluid within the primarychannels. This mixing helps insure a uniform distribution of residencetime of the fluid in the reactor, thus increasing the reactorefficiency. Jet impingement of fluid from secondary channels ontoreactor walls increases heat transfer at reactor walls.

When well-mixed flow passes through a relatively short secondarychannel, the reaction rates with the catalyst therein are higher due tothe relative lack of a boundary layer. The secondary channels actessentially as plug flow reactors.

When inlet fluids preferentially flow from one well-mixed primarychannel to another, the reaction with the catalyst in the correspondingsecondary channels is more efficient. The system acts as a series ofalternating plug flow reactors and well-stirred reactors.

By keeping at least some of the ends of the primary channels open, thepressure drop of the flow through the reactor is kept to a minimum.

By preferentially directing the fluid flow to or from a reactor wall,the heat transfer at the wall is increased. This higher heat transferhelps keep endothermic reactions warmer and exothermic reactions cooler.A more homogeneous temperature within the reactor increases catalyticselectivity.

Alternate Embodiments

FIG. 4 illustrates the transverse cross section of alternate embodiment400. At least one primary channel 406 is open at both the inlet 402 ofthe reactor and the outlet 404 of the reactor.

FIG. 5 illustrates the transverse cross section of alternate embodiment500. At least one primary channel 506 is open at either the inlet 502 ofthe reactor or the outlet 504 of the reactor. Additionally, at least oneprimary channel 508 is blocked at both ends.

FIG. 6 illustrates the transverse cross section of alternate embodiment600. At least one primary channel 606 is at an angle of more than 0degrees and less than 90 degrees to at least a portion 604 of thereactor wall.

FIG. 7 illustrates the transverse cross section of alternate embodiment700. At least one primary channel 706 is blocked by a portion 702 of areactor wall that is at an angle to primary channel wall 704. The anglemay be 90 degrees.

FIG. 8 illustrates the transverse cross section of alternate embodiment800. At least the inlet face 802 or outlet face 806 of the monolith isat an angle other than 90 degrees with respect to a portion 804 of areactor wall.

FIG. 9 illustrates the transverse cross section of alternate embodiment900. All primary channels 902 are open at both their inlets and outletsand are not parallel to the reactor wall 904 and are not normal to inletface 912 or outlet face 914.

FIG. 10 illustrates the transverse cross section of alternate embodiment1000. One portion 1002 of the reactor wall is not parallel to anotherportion 1004 of a reactor wall.

FIG. 11 illustrates the transverse cross section of alternate embodiment1100. The reactor wall 1102 has a conical shape.

FIG. 12 illustrates the transverse cross section of alternate embodiment1200. Primary channels 1206 are parallel to reactor walls 1204. The face1202 of the monolith is at an angle other than 90 degrees with respectto the reactor wall 1204 and the reactor axis 1210. The reactor axis1210 is parallel to the axis 1212 of at least one primary channel. Theaxis of the reactor may be parallel to all of the axes of the primarychannels.

FIG. 13 illustrates the transverse cross section of alternate embodiment1300. Both ends of all primary channels 1302 are blocked by reactor wall1304. Reactor wall 1304 is not normal to the primary channel walls andhas a bend in it.

Secondary Channels

FIG. 14 illustrates embodiment 1400 of a secondary channel. FIG. 14Ashows a plan view of the secondary channel. FIG. 14B shows a crosssection of the secondary channel.

Referring to FIG. 14A, the secondary channel is a cylindrical hole in aprimary wall 1408 with a maximum width W. The inside of the hole iscoated with catalyst 1406. Portions of the primary channel wall may alsobe coated with catalyst.

Referring to FIG. 14B, the length of the hole, T, is equal to thethickness of the primary channel wall.

It is preferred that the width W of the hole be less than or equal to 2times the thickness T of the primary channel wall 1408. In this way,forming the hole will result in a net increase of surface area of theprimary plus secondary channel wall area. If both the primary andsecondary channel walls are coated with catalyst, then adding holes witha width W less than or equal to 2 times the thickness Th of the primarychannel wall will result in more catalyst surface area per unit volumeof monolith.

The hole may be straight through the wall, at an angle to the wall, orin a serpentine configuration. As used herein, we define the tortuosityof a secondary channel as the ratio of the length of a hole to thethickness of the primary channel. Straight holes normal to the primarychannel wall have a tortuosity of 1. The porosity of sintered metal orceramic powders or of porous foams can be 5 or more.

Suitable tortuosity is less than 2. Low tortuosity is preferred since itminimizes the pressure drop of fluid flowing through the secondarychannel. Additionally, shorter holes have less length for boundary layerdevelopment and hence have higher mass and heat transfer to and from themonolith and higher reaction rates with the catalyst.

FIG. 15 illustrates alternate designs of secondary channels.

FIG. 1SA illustrates a plan view 1502 and cross sectional view 1504 of ahole drilled through a primary channel wall. The hole may be made byconventional means including mechanical drilling, etching and laserdrilling.

FIG. 15B illustrates a plan view 1512 and cross sectional view 1514 ofholes punched through a primary channel wall. The punching actioncreates a bur 1516 around a hole. The burr can be preferred due to thefact that it creates more secondary channel surface area for a givendiameter of the hole.

FIG. 15C illustrates a plan view 1522 and cross sectional view 1524 of aslit in a primary channel wall. The slit may be formed by conventionalmeans, such as stamping. The slit is characterized by a maximum width W1526 and a hydraulic diameter d₂ 1528.

As used herein, the hydraulic diameter of an opening is equal to 4 timesthe open area of an opening divided by the perimeter of the opening.

The dotted circles in FIGS. 15C and 15D indicate how big a circular holewould be of the same hydraulic diameter as the indicated opening. Thedotted circles do not form part of the invention.

FIG. 15D illustrates a plan view 1532 and cross sectional view 1534 of across hole in a primary channel wall. The cross hole may be formed byconventional means, such as a punch. The cross hole is characterized bya maximum width W 1536 and a hydraulic diameter d₂ 1538.

FIG. 16 illustrates generic detail of a relationship of a reactor, aprimary channel and secondary channels contained in the primary channelwalls. A honeycomb monolith 1600 is placed in a reactor 1604. Thereactor has a cylindrical cross section. The monolith comprises primarychannels 1606. Only one primary channel is shown. Other primary channelslie adjacent to the illustrated primary channel and are parallel to it.The primary channels fill the cross section of the reactor.

Primary channel 1606 has an axis 1610. The axis is inclined at angle θwith respect to the axis 1612 of the reactor.

The primary channel shown in FIG. 16 is shown in partial cutaway mode toshow the secondary channels terminating on the inside of the primarychannel.

Reactor Design Criteria

For a reactor of given external dimensions, the present inventionprovides designs to achieve minimal reactor pressure drop or to achieveenhanced mixing and heat transfer at relatively higher reactor pressuredrop.

To achieve a low pressure drop for a reactor, it has been found that asuitable design is given by the expression:$\theta = {\arctan\left\{ \left\lbrack \frac{P \cdot \left( {1 - P} \right) \cdot {GSA} \cdot d_{1} \cdot d_{2}}{K_{1} \cdot \tau \cdot T} \right\rbrack^{\frac{1}{3}} \right\}}$where θ is the angle of inclination of the axis of a primary channelwith respect to the axis of the reactor. P is the fraction of primarychannel wall that is perforated by secondary channels. GSA is thesurface area of the primary channel walls if the primary channel wallsare not perforated. d₁ is the hydraulic diameter of the primary channel.d₂ is the hydraulic diameter of the secondary channels. K₁ is a constantin the range of 0.2 to 20. K₁ is preferably in the range of 0.5 to 10.K₁ is more preferably about 2. τ is the tortuosity of the secondarychannels. T is the thickness of the wall of the primary channel.

To enhance heat transfer between fluid and the reactor wall it has beenfound that a suitable design criteria is given by the expression:$\theta = {\arctan\left\{ \left\lbrack \frac{P \cdot \left( {1 - P} \right) \cdot {GSA} \cdot d_{1} \cdot d_{2}}{K_{2} \cdot \tau \cdot T} \right\rbrack^{\frac{1}{3}} \right\}}$where K₂ is a constant in the range of 0.01 to 1.5. K₂ is preferably inthe range of 0.05 to 0.5. K₂ is more preferably about 0.2.

Table 1 illustrates the use of these expressions for calculating θ. Datais presented in Table 1 for Example 1 and Example 5. TABLE 1 Example 1Example 1 upper lower Variable Definition monolith monolith Example 5 d₁Primary channel hydraulic 5.4 mm 17.2 mm 2.4 mm diameter d₂ Secondarychannel hydraulic 134 micron 3.45 mm 27 micron diameter K Multiplier K₁= 2 K₂ = 0.2 K₁ = 2 τ Tortuosity of secondary channels 1 1 1 P Fractionof primary channel wall 0.14 0.23 0.12 that is perforated or open due tosecondary channels T Thickness of primary channel 329 micron 4.0 mm 81micron wall θ Angle of incidence of the primary 25 degrees 55 degrees 23degrees channel axis with respect to the reactor axis. GSA Geometricsurface area of primary 734 m²/m³ 232 m²/m³ 1648 m²/m³ channel walls ifthey were unperforated

EXAMPLE 1

The example reactor comprises a steam reforming catalytic reactorcomprising an upper monolith and a lower monolith. Each monolith isdesigned similarly to the monolith illustrated in FIG. 17, but withoutcentral column 1720 or spacers 1726. See Example 2 below for a moredetailed description of the monolith in FIG. 17.

The monoliths are constructed of wire cloth. The wires are made ofstainless steel or other material suitable for service in a steamreforming application. Pieces of wire cloth are corrugated with asinusoidal pattern. Smooth and corrugated coated wire cloths are layeredalternately and formed into frusta cones similar to those shown in FIG.17 converging towards the reactor outlet. The smooth cones extend fromtheir apexes to the reactor wall. The corrugated cones extend from thereactor wall to a distance of about 5 mm from the reactor axis and aretrimmed to be flush with the reactor wall. The apexes of the cones pointtowards the exit of the reactor.

The reactor wall is a tube of circular cross section. The material is ahigh temperature metal alloy known to be suitable for a steam reformingapplication. The reactor has an inside diameter of 100 mm, an outsidediameter of 120 mm and a length of 12 meters.

The upper monolith uses wire of 230 micron diameter. The spacing in boththe warp and weft of the wire cloth is 28 wires per cm. Catalystsuitable for steam reforming is applied to the wire cloth by thermalspraying such that the coating is about 50 microns thick on the sides ofthe wires parallel to the surface of the wire cloth and is less than 5micron thick on the sides of the wires normal to the cloth surface.About 14% of the cloth surface is open. The cloth thickness andsecondary channel length are considered to be approximately 330 microns.The secondary channels have hydraulic diameters of approximately 134microns.

The upper monolith is designed to provide a total surface area of boththe primary and secondary channels of 1,500 m²/m³. θ is chosen tominimize the pressure drop through the top portion of the steamreformer. The upper monolith has sinusoidal corrugations with a 4.5 mmheight difference from peak to trough and 4.5 mm wavelength. The primarychannel hydraulic diameter is 5.4 mm. The GSA of the primary channels isapproximately 734 m²/m³. Using a value of 2 for K₁ and a tortuosity of1, the angle θ of the frusta cones to the reactor axis is 25°.

The lower monolith is designed to provide jet impingement cooling of thereactor wall by increasing the fluid velocity along the secondarychannels and directing the jets emerging from secondary channels towardthe reactor wall. The total surface area of the primary and secondarychannels is designed to be 370 m²/m³.

The lower monolith uses wire of 3.8 mm diameter. The spacing in both thewarp and weft of the wire cloth is 1.4 wires per cm. Catalyst suitablefor steam reforming is applied to the wire cloth by thermal sprayingsuch that the coating is about 100 microns thick on the sides of thewires parallel to the surface of the wire cloth and is less than 5micron thick on the sides of the wires normal to the cloth surface.About 23% of the cloth surface area is open. The cloth thickness andsecondary channel length are considered to be approximately 4.0 mm. Thesecondary channels have hydraulic diameters of approximately 3.45 mm.

The lower monolith comprises sheets with sinusoidal corrugations. Thecorrugations have a 10 mm height difference from peak to trough and 25mm wavelength. The primary channel hydraulic diameter is 17.2 mm. TheGSA of the primary channels is approximately 232 m²/m³. Using a value of0.2 for K₂ and a tortuosity of 1, the angle θ of the frusta cones to thereactor axis is 55°. Jets emerging from secondary channels and impingingthe reactor wall have initial velocities 5 times as high as the velocityof fluid flowing along the primary channels. The initial jet hydraulicdiameters are 3.45 mm and the jets project 0 mm to 10 mm to impinge thereactor wall at center-to-center spacings averaging approximately 10 mm.

In operation, the outside of the reactor wall is heated by combustion.Heat transfer to the outside of the wall is enhanced by enriching thecombustion air to at least 35% oxygen by volume. The combustion oxidantmay have an oxygen content as high as 100% by volume. The fuel can bemethane or other hydrocarbon.

The high oxygen content of the oxidant relative to air increases heattransfer relative to air by creating a higher radiant flame temperatureand longer residence time for the combustion products inside acombustion chamber that the reactor is located in. Multiple reactors maybe located in the same combustion chamber.

The combustion chamber may be at a pressure greater than one atmosphere.

EXAMPLE 2

FIG. 17 illustrates longitudinal and transverse cross sections of asecond example 1700 of the invention. The example is a catalyticconverter and has an inlet 1750, an outlet 1752, a monolithic substrate1760 and cylindrical reactor wall 1708. Monolithic substrate 1760 isconstructed of alternating corrugated sheets 1704 and smooth sheets1702. The alternating sheets may either be in the form of alternatingsmooth and corrugated nested cones or of interleaved smooth andcorrugated helixes at an oblique angle to the reactor axis. The spacesbetween corrugations and smooth sheets define primary channels 1706.

The corrugated and smooth sheets are inclined at an oblique angle toconverter axis 1762. Thus, at least one primary channel 1716 is blockedat one end by reactor wall 1708.

Example 1700 further comprises optional central column 1720. Centralcolumn 1720 comprises center rod 1724 and frusta-conical spacers 1726.The spacers interleave the smooth sheets to support the monolith againstaxial forces imposed by fluid flow 1780. The corrugated sheets do notinterleave the spacers.

Both the smooth and corrugated sheets are perforated to providesecondary channels (not shown). The perforations are round in shape andhave diameters in the range of 20 to 30 microns.

The smooth sheets and corrugated sheets are formed of metal foil. Thesheets are coated with a catalyst.

The corrugated sheets have a corrugation wavelength which increases withdistance from the central rod. The wavelength increases less thanproportionally to the distance from the central rod.

In an alternate embodiment, there is no central column 1720. The smoothsheets converge at the axis of the reactor. The corrugated sheets areopen at the axis of the reactor.

The reactor functions with fluid entering either the inlet 1750 or theoutlet 1752.

The reactor may comprise baskets which are secured to the reactor wallsand which serve to hold the monolith in place.

EXAMPLE 3

FIG. 18 illustrates transverse and longitudinal sections of alternateexample reactor 1800. The reactor comprises an inlet 1850, outlet 1852,cylindrical reactor wall 1808 and monolith 1810. The monolith comprisesalternating smooth sheets 1802 and corrugated sheets 1804. Portions ofone each of the smooth and corrugated sheets are shown bold for clarity.The bold appearance does not form part of the invention. The layers ofsheets are arranged radially and meet at or near a central core 1806.The spaces between the sheets are the primary channels.

A hollow conduit 1840 may be present in the center of the monolith. Thehollow conduit will be discussed in more detail in the section“Additional Features” of the present application.

The primary channels are inclined at an angle with respect to thereactor walls such that at least some of the primary channels areblocked at one end and open at the other end. The angle of inclinationbetween the primary channels and the axis 1806 of the reactor walls isabout 30 degrees. The angle of inclination can be in the range ofgreater than 0 degrees and less than 90 degrees.

Both the smooth sheets and the corrugated sheets are perforated withholes of about 30 microns in diameter to form the secondary channels(not shown). The portion of the area of the primary channel walls thatis open is 30%.

FIG. 20 provides more detail of how the monolith of this example isformed. In FIG. 20A, smooth sheet 2002 is placed next to corrugatedsheet 2004 and bent about bend line 2006 with the corrugations at anoblique angle to the bend line 2006 to form leaf assembly 2000. In FIG.20B, first leaf assembly 2012 is placed inside second leaf assembly 2014to form nested leaf assembly 2010. Additional leaf assemblies are addedto the nested leaf assembly until the nested leaf assembly is full.Corrugations on a given side of all nested assemblies are parallel toeach other.

A single sheet (not shown) of smooth substrate without perforations maybe inserted in the center of each nested leaf assembly. This separatesthe oppositely inclined corrugated sheets. The single unperforated sheetmay be of greater thickness than the other sheets to stiffen the nestedleaf assembly. The single unperforated sheet may be coated with catalystand catalyst support material.

Several nested leaf assemblies are then joined side by side at bend line2006 to form the monolith. Bend line 2006 runs along the reactor axis1806 or next to the central hollow conduit 1840 (FIG. 18).

All of the sheets and assemblies may be joined to each other or to thereactor wall by brazing. The braze material may be coated on the sheetmaterials prior to forming and assembly.

FIG. 21 shows how a corrugated sheet might be formed. FIG. 21A shows asheet material 2100 first folded into an accordion shape. FIG. 21B showsthe sheet material after it has next been partially stretched into itsfinal form. FIG. 21C shows the sheet material after it has lastly beenfully stretched into its final form

FIG. 23 shows a plan view of a corrugated sheet 2300 similar to that ofFIG. 21C. The sheet is formed of a mesh material thus creating numeroussecondary channels 2306. The axes 2304 of the primary channels 2308 areat an angle θ with respect to the bend line 2302. The maximum width ofthe primary channels at the wall is W.

Secondary channels may be formed in the sheets, and catalyst may beplaced in the secondary channels before the sheets are formed into theirsmooth or corrugated forms. Substrate coating for catalyst support maybe applied by dipping in a slurry, thermal spraying or other knownmeans.

The monolith and the reactor walls may be made of high temperature metalalloy, such as stainless steel.

The monolith may also be an extrusion. The monolith may be made ofceramic, such as cordierite or alumina.

FIG. 22 illustrates how the angling of the primary channels with respectto the reactor axis causes the fluid to pass unidirectionally throughthe secondary channels. FIG. 22 is a small portion 2200 of alongitudinal cross section of a reactor similar to reactor 1800 (FIG.18). The reactor is constructed with smooth sheets 2212 and sharp anglecorrugated sheets 2210. The overall flow direction is 2202. The anglingof the primary channels with respect to the axis of the reactor at leastin part causes secondary channel flow 2204 to proceed from one primarychannel 2222 to an adjacent primary channel 2224. For reactors wherethere is only catalyst in the secondary channels, the fluid beingprocessed experiences successive reactions with catalyst as plug flow inthe secondary channels and mixing in the primary channels. Thus thereactor may be described as a series of successive alternating plug flowreactors and well-stirred mixers. The number of primary channels that agiven portion of fluid passes through can be considered as the number ofstages of reaction plus mixing that the fluid passes through.

EXAMPLE 4

FIG. 19 is a perspective view of alternate embodiment 1900 of thepresent invention. Embodiment 1900 comprises alternating layers oftapered corrugated sheets 1910 and smooth sheets 1912. Primary channelsare formed by the spaces between the sheets. Secondary channels (notshown) are formed by perforating both the smooth sheets 1912 and thecorrugated sheets 1910. Secondary channels could also be formed byperforating only the corrugated sheets or only the smooth sheets.

Only one corrugated and one smooth sheet is shown in FIG. 19 forclarity.

In this embodiment, flow through the secondary channels results from therelatively large inlets 1902 of some primary channels and the relativelysmall outlets 1904 of the same channels. Hence said primary channelsdecrease monotonically in cross sectional area.

Flow through the secondary channels is further promoted by thecorresponding relatively small inlets 1906 and large outlets 1908 of theprimary channels adjacent to the primary channels with large inlets andsmall outlets. Hence these primary channels increase monotonically incross sectional area.

No primary channels need to have one end completely blocked in order tofor this embodiment to be effective. In the embodiment 1900 in which theconvergent ends of primary channels are blocked, the present inventionis useful as a particulate trap, such as in catalytic converters fordiesel engine exhaust aftertreatment. The ends may be blocked by aporous or nonporous material or by virtue of the primary channelconvergence zero cross sectional area.

EXAMPLE 5

A catalytic converter is formed according to the embodiment illustratedin FIG. 18. The catalytic converter is suitable for treatment ofinternal combustion engine exhaust gases containing CO, hydrocarbons andNOx. The internal combustion engine may power a vehicle.

The primary channel wall consists of wire cloth with 51 micron diameterwires of stainless steel spaced 130 wires per cm in both warp and weft.The catalyst and associated support is suitable for internal combustionengine exhaust gas aftertreatment. The catalyst support is applied tothe wire cloth by thermal spraying such that the coating is 15 micronthick on the sides of the wires parallel to the surface of the cloth andis less than 5 micron thick on the sides of the wires normal to thecloth surface. 12% of the cloth surface area is open. The cloththickness and secondary channel lengths are considered to beapproximately 81 micron. The secondary channels have hydraulic diametersof approximately 27 micron.

Some pieces of wire cloth are corrugated with a sinusoidal pattern.Smooth and corrugated coated wire cloths are layered alternately andformed into 6 nested leaf assemblies, with each nested leaf assemblyenclosing a 60° angle. The reactor wall is a tube of circular crosssection with an inside diameter of 125 mm and a length of 125 mm.

The reactor is designed to provide a total surface area of the primaryand secondary channels of 3,700 m²/m³ while minimizing the pressuredrop. The maximum difference in height from corrugation troughs to peaksis 2 mm at the reactor wall and the corrugation wavelength is 2 mm atthe reactor wall. The GSA of the primary channels without its secondarychannels is approximately 1,650 m²/m³, and the average primary channelhydraulic diameter is about 2.4 mm. Using a value of 2 for K₁ and atortuosity of 1, the angle of the corrugations to the reactor axis is23°.

Six nested leaf assemblies are formed each with a single solid sheet attheir centers. The single solid sheets are 80 microns thick with a 15micron thick coating of catalyst support.

Adjacent sides of nested leaf assemblies have parallel primary channels.

The six nested assemblies are joined side by side about a common bendline to form a monolith. The monolith is slightly flexed or rotated tocompressively fit inside the converter walls. The monolith fills thereactor cross section.

The portion of the area of the reactor cross sectional area that isopen, referred to herein as the “open face area” or OFA, is about 95%.

A finely divided noble metal catalyst is deposited on the catalystsupport using conventional means. Exhaust gas from an internalcombustion engine is passed through the reactor. The hydrocarbons, NOxand CO in the exhaust gas are converted to carbon dioxide, nitrogen andwater.

EXAMPLE 6

A reactor is designed similar to the reactor of Example 5 above, butwith holes punched in 80 micron thick solid sheets to form secondarychannels. The holes have 10 micron long burrs on their ends.

EXAMPLE 7

The reactor of Example 5 is combined with a bypass valve in anautomotive exhaust. The bypass valve diverts input gases through abypass pipe to a midsection of the monolith. The bypass is activated,causing fluid to bypass the initial section of the monolith, when thetemperature in the inlet of the monolith reaches a certain maximumthreshold. Alternatively, the bypass may be activated after a certainpredetermined period of time subsequent to the start of the automobile.

Cooling means, such as a heat exchanger, may be provided in the bypasspipe to cool the exhaust gases before they enter the midsection of themonolith. In this manner, the temperature of the monolith remains belowa certain threshold such as the sintering temperature of the catalyst orits substrate.

Similar combination of reactor and bypass pipe may be designed with theratio of the width of the reactor to the length of the reactor less thanor equal to one.

The reactor may comprise at least one other structure comprising acatalyst where the bypass pipe introduces gas between the monolith andthe at least one other structure. The structure may be a monolithaccording to the present invention. The structure may also be acontainer of catalyst beads.

The structure may be a microlith such as that described in U.S. Pat. No.5,051,241 to Pfefferle and incorporated herein by reference. The reactormay incorporate a bypass valve and bypass pipe to bypass the microlithand pass fluid directly through the monolith of the present invention.

EXAMPLE 8

A reactor according to Example 5 is constructed except that there is nocatalyst on the monolith. The reactor serves to efficiently anduniformly heat the fluids flowing therein. Alternatively, the fluidswithin the reactor may be at higher temperature than the ambient andhence the reactor serves to cool the fluids.

Additional Features

The present invention can be modified in several ways to create usefuleffects.

In one embodiment, the secondary channels may be non-uniformlydistributed over the walls of the primary channels such that the flow ofprocess fluids may be directed towards or away from the reactor walls atvarious locations. For example, in single row, multi-tube steamreformers, some sides of the reactor tubes face a source of combustionand hence have a higher heat flux than other sides. The secondarychannels in combination with the inclined primary channels can bedesigned to direct the flow to the side of the reactor with the highheat flux more than to the other sides. Thus the convective heattransfer coefficient at the sides of the reactors with the high heatflux can be made relatively higher than at the other sides.

In other embodiments, the combination of the primary and secondarychannels can be designed such that the process fluid flows in a helicalor other desired path within the converter.

The distribution of the secondary channels can be adjusted such that theprocess fluids flow alternately towards and away from the reactor walls.For example, referring to FIG. 17 unless otherwise indicated, a firstseries of at least one of either the corrugated sheets 1704 or smoothsheets 1702 may have a relatively lower resistance to flow, such as ahigher density of secondary channels near the reactor wall 1708. Thus arelatively large proportion of the process fluid in the reactor willflow near the reactor wall when it impinges on said first at least onesmooth or corrugated sheet. Similarly, a second series of at least oneof either the corrugated sheets 1704 or smooth sheets 1702 may have arelatively lower resistance to flow, such as a higher density ofsecondary channels near the converter axis 1762. Thus a relatively largeproportion of the process fluid in the reactor will flow near theconverter axis when it impinges on said second at least one smooth orcorrugated sheet. By alternating said first and said second series ofsheets, the process fluid can be made to alternately flow near thereactor wall and near the reactor axis. This flow pattern significantlyincreases the heat transfer with the reactor walls. By adjusting theconcentration of secondary channels near the reactor axis or reactorwalls relative to the concentration of the secondary channels in therest of the primary channels, the designer can adjust desiredcombinations of high heat transfer (high concentration of secondarychannels near the reactor walls and axis) and low pressure drop (uniformconcentration of secondary channels along primary channels). In oneextreme, the secondary channels are found only near the reactor walls orthe axis. In the other extreme, the secondary channels are distributeduniformly along the primary channels.

Similar effects can be achieved by varying the diameters of thesecondary channels.

In an alternate embodiment, the thickness of the catalytically activecoating on the monolith can be varied as a function of the localreaction rates. For example, the present invention may be used as areactor in a steam reformer. Catalyst is applied to at least the wallsof the secondary channels as finely divided material on a porous supportstructure. Fluids at the inlet of a steam reformer reactor are at arelatively low temperature such that the activity and surface area ofthe active catalyst constrains the overall reaction kinetics. In suchsituations the catalytically active material participates in the desiredreaction at greater depths within the pores of its support structure.Near the inlet of the reactor, therefore, it is preferred to applythicker catalyst support material of 50 to 300 microns to the monolith.In downstream locations in the said reactors the temperatures arehigher, making the catalyst more active at the outer surfaces of thecatalyst support structures such that thinner coatings of catalyst of 10to 100 microns may be applied as a function of the thermal profile inthe reactor. Similarly, the coating thicknesses may be thinner near thewalls of the reactor, where temperatures are higher. Thicker coatingsmay be applied near the axis of the reactor.

In another alternate embodiment, thermal conduction through the catalystsupport material and the thermal conduction along the length of thesubstrate the catalyst support material is applied to may be variedindependently. Coating a relatively thick substrate of high thermalconductivity and of a substantially direct thermal path from theconverter wall to the converter axis with a relatively thin catalyticsupport material of low conductivity, favors better heat transferbetween the catalyst wall and the interior of the converter. Forreactors according to the present invention for treating exhaust gasesof internal combustion engines, this configuration helps keep thetemperature more uniform in the reactor to minimize overheating at thereactor axis.

For reactors according to the present invention used in steam reforming,the transfer of heat from the reactor wall to the more central portionsof the reactor prevents local overheating of hydrocarbons that couldprecipitate carbon. The carbon can foul the catalyst.

Conversely, coating a relatively thin substrate of low conductivity witha catalytic support material of relatively high resistance to thermalconductivity, favors the local transfer of heat between the reactor walland process fluids nearer the reactor wall.

In another alternative embodiment, the angle of the primary channels tothe axis of a reactor may be adjusted to alter the view factor forradiant heat transfer between the reactor walls and the interior of themonolith. If the view factor is large, such as by a relatively largeangle, then heat transfer by radiation to the interior of the monolithis improved.

In another alternative embodiment, reactors designed according to thepresent invention may comprise a hollow column which conveys relativelyunreacted inlet fluids to interior portions of the monolith. Hollowcolumns may also be designed such that reacted fluids are removed frominterior portions of the monolith.

For example, referring to FIG. 18 unless otherwise specified, a reactorsimilar to reactor 1800 is designed with an additional central conduit1840 therein. The conduit is coincident with the axis 1806 of thereactor. The reactor is used for steam reforming.

The conduit conveys at least a portion of the inlet fluid comprisinghydrocarbons to one or more designated positions along the length of thecatalytic converter thus shielding the portion of inlet fluids fromimmediate exposure to the relatively high temperature reactor walls. Bywithholding a portion of the hydrocarbons from exposure to the heatedtube walls, the remainder of the inlet fluids have a higher ratio ofsteam to carbon and a higher heat flux through the tube walls can beaccommodated without carbon precipitation. By introducing the withheldhydrocarbons downstream in the monolith, desirably high ratios of carbonto steam may be obtained overall. This permits increased throughput anddecreased the steam export.

The central conduit may distribute inlet fluids into the surroundingmonolith via lateral holes in the central conduit. The inlet fluidsreact with the steam present in the monolith which increases the heatload on the said downstream portions of the reactor.

By withholding a portion of the hydrocarbons from the monolith at thereactor inlet, the reactor has a lower thermal load at the inlet and amore uniform thermal profile from inlet to outlet for optimal operatingtemperatures. Further, the inlet fluids conveyed by the central conduitencounter less pressure drop than if conveyed through dispersedcatalytic surfaces, saving compression energy.

The inlet fluids introduced via the central conduit may be at a lowertemperature than the monolith. The conduit may also thermally insulatethe fluid it conveys from the monolith, helping to preserve the lowtemperature of the inlet fluids to help level the thermal load on thereactor and maintain a uniform temperature profile.

The central conduit may be used to remove hydrogen from the processfluids to permit more complete reaction of hydrocarbons to hydrogen. Thecentral conduit may comprise a hydrogen permeable membrane, such aspalladium or platinum.

In another alternative embodiment, a reactor according to the presentinvention comprising alternating smooth and corrugated sheets may havesaid sheets with different thicknesses. For example, the smooth sheetsmay be thicker or otherwise made stronger than the corrugated sheets.

This invention may be used as a mixer or emulsifier.

The inlet fluid to the invention may be a mixture of liquid and gas or amixture of immiscible liquids.

If a monolith according to the present invention is to be inserted intotubing which has a rough or irregular surface and if radial heattransfer is desired, the primary channel walls may be slit in theportions adjacent to the tubing such that monolith can deform to theshape of the tube and thus effect good radial heat transfer.

The monolith of the present invention may be compressed within acompression sleeve for mounting or retrofitting the monolith into tubes.The compression sleeve may be a material that volatizes during use,allowing the monolith to expand and conform to the rector walls. Thecompression sleeve may also be a brazing material which may be coatedwith a fluxing material. If fluxing material is used on the outersurface of the sleeve, the sleeve may be a perforated sheet, net, mesh,powder metal or otherwise permeable surface. Before service the reactoris heated to melt the brazing material and thus attach the monolith tothe reactor wall.

At increased angles between the reactor axis and the primary channelsand for monoliths compressed as described above, the primary channelswill increasingly act as load bearing beams to provide compression ofthe monolith against the reactor walls. The compression of the monolithshould not exceed the yield strength or creep strength of the substratefor the anticipated temperature exposure of the reactor duringmanufacturing, storage and service.

Having thus described the invention with particular reference to theembodiments thereof, it will be obvious that various changes andmodifications can be made therein without departing from the spirit andscope of the present invention as defined in the appended claims.

1. A reactor comprising: an inlet; an outlet; a reactor wall; and amonolith wherein said monolith comprises primary and secondary channels;at least one of the primary channels is parallel to each of at leastthree other primary channels; said at least one primary channel isconnected to each of the other of the at least three primary channels byat least some of the secondary channels; the axis of the at least oneprimary channel is at an angle with respect to a portion of the reactorwall such that the angle is in the range of more than 0 degrees and lessthan 90 degrees; at least one of the primary channels is open at both ofits ends; and said monolith is placed within said reactor such that atleast a portion of a fluid entering the inlet of the reactor willsubsequently pass through the monolith and then exit the reactor throughthe outlet.
 2. The reactor of claim 1 wherein the hydraulic diameter ofat least one of said secondary channels is in the range of 1 micron to100 microns.
 3. The reactor of claim 1 wherein the combined surface areaof the secondary channels is greater than the combined surface area ofthe primary channels.
 4. The reactor of claim 3 wherein the hydraulicdiameter of at least one secondary channel is less than twice thethickness of the portion of the wall of the primary channel that saidsecondary channel passes through.
 5. The reactor of claim 1 whichfurther comprises a catalyst wherein the catalyst is attached to thewall of at least one secondary channel.
 6. The reactor of claim 5wherein the catalyst is suitable for reducing the concentration of atleast one pollutant in a vehicle exhaust stream.
 7. The reactor of claim5 wherein the catalyst is suitable for steam reforming.
 8. The reactorof claim 5 which further comprises a combustion chamber wherein thecombustion chamber at least partially surrounds the reactor wall.
 9. Thereactor of claim 8 which further comprises at least one burner whereinthe burner is adapted to use a gas with more than 20% oxygen as anoxidant and wherein the burner is adapted to heat the reactor wall. 10.The reactor of claim 8 where the combustion chamber is adapted tooperate at a pressure greater than one atmosphere.
 11. The reactor ofclaim 5 which further comprises a bypass valve and bypass pipe which isconfigured such that at least a portion of a fluid entering the reactorcan be diverted past an initial section of the monolith.
 12. The reactorof claim 5 which further comprises a bypass valve, a bypass pipe and atleast one other structure comprising a catalyst, wherein the bypassvalve and bypass pipe are configured such that at least a portion of afluid entering the reactor can be diverted past either the monolith orsaid at least one other structure.
 13. The reactor of claim 12 whereinsaid at least one other structure is a microlith, said microlith isupstream of said monolith and said bypass valve and said bypass pipe areconfigured to divert a portion of a fluid past said microlith andthrough said monolith.
 14. The reactor of claim 1 wherein at least aportion of the primary channels comprise walls which are formed bystretching a folded piece of metal.
 15. The reactor of claim 1 whereinthe combined open face area of the secondary channels is greater than50%.
 16. A reactor having an axis, said reactor comprising: an inlet; anoutlet; a reactor wall; and a monolith wherein said monolith comprisesprimary and secondary channels; at least one of the primary channels isparallel to each of at least three other primary channels; said at leastone primary channel is connected to each of the other of the at leastthree primary channels by at least some of the secondary channels; theaxis of at least one primary channel is at an angle with respect to thereactor axis such that the angle is in the range of more than 0 degreesand less than 90 degrees; at least one of the primary channels is openat both of its ends; and said monolith is placed within said reactorsuch that at least a portion of a fluid entering the inlet of thereactor will subsequently pass through the monolith and then exit thereactor through the outlet.
 17. A reactor having an axis, said reactorcomprising: an inlet; an outlet; a reactor wall; and a monolith whereinsaid monolith comprises primary and secondary channels; the walls ofsaid primary channels comprise a coating such that said coating isthicker on the primary channel walls than on the secondary channelwalls; said monolith is placed within said reactor such that at least aportion of a fluid entering the inlet of the reactor will subsequentlypass through the monolith and then exit the reactor through the outlet.18. A reactor comprising: an inlet; an outlet; a reactor wall; and amonolith wherein said monolith comprises primary and secondary channels;at least three of the primary channels are parallel to each other; eachone of said at least three primary channels is connected to each of theother of the at least three primary channels by at least some of thesecondary channels; the tortuosity of the at least some of the secondarychannels is less than 2 the axis of at least one primary channel is atan angle with respect to the reactor axis such that the angle is in therange of more than 0 degrees and less than 90 degrees; and said monolithis placed within said reactor such that at least a portion of a fluidentering the inlet of the reactor will subsequently pass through themonolith and then exit the reactor through the outlet.
 19. A reactorhaving an axis, said reactor comprising: an inlet; an outlet; a reactorwall; and a monolith wherein said monolith comprises primary andsecondary channels; the axis of at least one of said primary channels isat an angle with respect to the axis of the reactor wherein said angleis about the value given by the expression$\arctan\left\{ \left\lbrack \frac{P \cdot \left( {1 - P} \right) \cdot {GSA} \cdot d_{1} \cdot d_{2}}{K_{1} \cdot \tau \cdot T} \right\rbrack^{\frac{1}{3}} \right\}$where K₁ is a value between 0.2 and 20; and said monolith is placedwithin said reactor such that at least a portion of a fluid entering theinlet of the reactor will subsequently pass through the monolith andthen exit the reactor through the outlet.
 20. The reactor of claim 19wherein K₁ is a value between 0.5 and
 10. 21. The reactor of claim 19wherein K₁ is about
 2. 22. A reactor comprising: an inlet; an outlet; areactor wall; and a monolith wherein said monolith comprises primary andsecondary channels; the axis of at least one of said primary channels isat an angle with respect to the axis of the reactor wherein said angleis about the value given by the expression$\arctan\left\{ \left\lbrack \frac{P \cdot \left( {1 - P} \right) \cdot {GSA} \cdot d_{1} \cdot d_{2}}{K_{2} \cdot \tau \cdot T} \right\rbrack^{\frac{1}{3}} \right\}$where K₂ is a value between 3 and 50; and said monolith is placed withinsaid reactor such that at least a portion of a fluid entering the inletof the reactor will subsequently pass through the monolith and then exitthe reactor through the outlet. Should we also restrict ourselves tojets impinging the reactor wall?
 23. The reactor of claim 22 wherein K₂is a value between 5 and
 25. 24. The reactor of claim 22 wherein K₂ isabout
 15. 25. A method for reacting a fluid with a reactor comprising:causing a fluid to enter the reactor through an inlet, said reactorcomprising; an inlet; an outlet; a reactor wall; and a monolith whereinsaid monolith comprises primary and secondary channels; at least one ofthe primary channels is parallel to each of three other primarychannels; each one of said at least one primary channel is connected toeach of the other of the at least three primary channels by at leastsome of the secondary channels; the axis of at least one of the at leastthree primary channels is at an angle with respect to a portion of thereactor wall such that the angle is in the range of more than 0 degreesand less than 90 degrees; the tortuosity of the at least some of thesecondary channels is less than 2 said monolith is placed within saidreactor such that at least a portion of a fluid entering the inlet ofthe reactor will subsequently pass through the monolith and then exitthe reactor through the outlet; and allowing the fluid to exit theoutlet of the reactor.
 26. The method of claim 25 wherein the reactionbetween the fluid and the reactor comprises heat transfer and atemperature of the fluid entering the reactor is different than atemperature of the reactor wall.
 27. The method of claim 25 wherein thereaction between the fluid and the reactor comprises a chemical reactionand at least one secondary channel comprises a catalyst whichaccelerates or retards the rate of said chemical reaction relative tothe rate of the chemical reaction in the reactor in the absence of saidcatalyst.
 28. The method of claim 27 wherein the fluid comprises theexhaust gas from a vehicle.
 29. The method of claim 27 wherein the fluidcomprises methane and water vapor and the chemical reaction comprisessteam reforming.
 30. The method of claim 25 wherein the monolith isdimensioned such that a portion of the fluid flows unidirectionallythrough at least one secondary channel.
 31. The method of claim 25 whichfurther comprises heating said reactor with the products of combustion.32. The method of claim 31 wherein the products of combustion areproduced by reacting a fuel with a gas comprising oxygen wherein theconcentration of oxygen in said gas is greater than 20%.
 33. The methodof claim 31 wherein the pressure of said products of combustion isgreater than one atmosphere.
 34. A reactor having an axis, said reactorcomprising: an inlet; an outlet; a reactor wall; and a monolith whereinsaid monolith comprises primary and secondary channels; at least a firsttwo of the primary channels are parallel to each other defining a firstplane; at least a second two of the primary channels are parallel toeach other, defining a second plane; at least a third two of the primarychannels are parallel to each other, defining a third plane; said atleast a first two primary channels are between said second plane andsaid third plane; none of said at least a first two primary channels areparallel to any of said at least a second two primary channels or saidat least a third two primary channels; at least a first portion of theat least a first two primary channels is connected to at least a portionof said at least a second two primary channels by at least a first oneof said secondary channels; at least a second portion of the at least afirst two primary channels is connected to at least a portion of said atleast a third two primary channels by at least a second one of saidsecondary channels; and said monolith is placed within said reactor suchthat at least a portion of a fluid entering the inlet of the reactorwill subsequently pass through the monolith and then exit the reactorthrough the outlet.
 35. A reactor comprising: an inlet; an outlet; areactor wall; and a monolith wherein said monolith comprises primary andsecondary channels; the cross sectional area of at least a first one ofthe primary channels increases monotonically with distance from thereactor inlet; the cross sectional area of at least a second one of theprimary channels decreases monotonically with distance from the reactorinlet; said at least a first one of the primary channels is connected tosaid at least a second one of the primary channels by at least a firstone of the secondary channels such that at least a first portion offluid entering the reactor is caused to flow from said at least a firstone of the primary channels to said at least a second one of the primarychannels; and said monolith is placed within said reactor such that atleast a portion of a fluid entering the inlet of the reactor willsubsequently pass through the monolith and then exit the reactor throughthe outlet.
 36. The reactor of claim 35 wherein the smaller end of atleast one channel primary channel is blocked by a porous or nonporousmaterial.
 37. A reactor having an axis, said reactor comprising: aninlet; an inlet face; an outlet; an outlet face; a reactor wall; and amonolith wherein said monolith comprises primary and secondary channels;at least the inlet face or the outlet face of at least one primarychannels is at an angle with respect to the axis of the said at leastone primary channel such that the angle is in the range of more than 0degrees and less than 90 degrees; at least one primary channel is openat both ends said monolith is placed within said reactor such that atleast a portion of a fluid entering the inlet of the reactor willsubsequently pass through the monolith and then exit the reactor throughthe outlet.